“Lingonberries ‘could prevent weight gain’,” says The Daily Telegraph, reporting on the so-called “superberries” from Scandinavia. But before rushing to your local Swedish grocer, it’s worth noting that these tests were done on mice…

“Lingonberries ‘could prevent weight gain’,” says The Daily Telegraph, reporting on the so-called “superberries” from Scandinavia. But before rushing to your local Swedish grocer, it’s worth noting that these tests were done on mice.

This research involved mice that were genetically engineered to become obese and develop features of diabetes.

In the experiment all the mice were fed a high fat diet for 13 weeks which was intended to mimic the fatty western diet. However, eight different groups of mice were given eight different types of freeze-dried berry alongside the fatty diet to see if this affected weight gain. Two further control groups received no berries – one eating the same high fat diet, and another a low fat diet.

Unsurprisingly, all the mice gained large amounts of weight due to the high diet, but some of those eating berries gained less.

Lingonberries, a wild fruit popular in Scandinavia, were the best of the bunch showing the lowest increase in body fat, cholesterol and blood sugar of all the high fat groups.

An obvious limitation is that the study has not looked at the effect of lingonberry consumption on body measures and health outcomes in humans. And crucially, mice fed lingonberries still put on weight with the high fat diet, just not as much. So if you are trying to lose weight, relying on any one food for weight control is not a wise or healthy approach.

Where did the story come from?

The study was carried out by researchers from Lund University in Sweden. Financial support was provided by the Antidiabetic Food Centre, the Swedish Research Council, the Swedish Diabetes
Association, the Royal Physiographic Society in Lund, and the Crafoord Foundation.

It may not count as a conflict of interest, but the lingonberry is reportedly the national fruit of Sweden and the country is understood to be the world’s largest producer of the fruit.

The study was published in the peer-reviewed Journal of Nutrition and Metabolism.

The UK media’s reporting of the study was accurate. While the headlines could have made more of the fact that the study involved mice not humans, both The Daily Telegraph and the Mail Online contain appropriate advice from the study’s authors. For example, the Mail quotes Lovisa Heyman as saying, “While the findings in mice are exciting, it should absolutely not be interpreted as a license to eat an unhealthy diet as long as you add lingonberries”.

What kind of research was this?

This was animal research looking at how effective eight different types of berries might be at preventing obesity and metabolic abnormalities associated with risk of type 2 diabetes such as blood sugar control and cholesterol levels.

In humans these changes in metabolism that increase obesity and diabetes risk are often referred to as metabolic syndrome.

To investigate the potential effects of the berries in humans, the researchers gave the berries to a group of genetically engineered mice predisposed to develop obesity and prediabetes. Prediabetes describes a situation where some, but not all, of the diagnostic criteria for diabetes are met. The mice were fed a high fat diet mimicking the modern western diet.

What did the research involve?

The researchers used six-week old mice genetically engineered to develop obesity and prediabetes. They were divided into 10 groups of 12 mice. For 13 weeks:

eight groups were fed a high fat diet (45% of calories from fat), supplemented with one of eight different freeze dried berries (lingonberry, blackcurrant, raspberry, bilberry, blackberry, crowberry, prunes or acai berry powder), which were freely available to them

one control group was fed a calorie-matched high fat diet without berries

one control group was fed a low fat diet (10% calories from fat) without berries

Body weight and food intake were monitored weekly. At the end of the study blood samples were assessed for sugar, insulin levels, cholesterol, and other fats. The researchers also examined body organs, including the liver and spleen to look at the amount of fat build-up.

What were the basic results?

The energy intake was similar across all groups of mice on the different diets except those eating blackcurrant and bilberries, who ate more food and calories. Exceptions aside, this means weight differences between the different groups are not because they were simply eating more.

From a similar starting weight of under 25g, after the 13 week diet, body weight gains were lowest in the low-fat control group (they now weighed 32g), followed by the lingonberry (33g), blackcurrant (36g), raspberry (37g) and bilberry (38g) groups. All of these groups had significantly higher body weight than the low fat control group. Meanwhile, the acai berry group had significantly higher body weight than the high fat controls (48g).

Mice who had been fed lingonberry, blackcurrant, and bilberry had lower overall body fat than the high fat controls eating no berries. The lingonberry group actually had equivalent body fat to the low fat control group. The lingonberry group also had significantly lower liver mass than the high fat controls.

Fasting blood sugar levels were significantly lower in the lingonberry and blackcurrant groups than the high fat controls. Both of these groups had glucose, insulin and insulin resistance levels very similar to the low fat diet group. The lingonberry, blackcurrant and low fat groups also had significantly lower total cholesterol levels than the high fat controls. Meanwhile the acai berry group tended to have higher cholesterol levels than the high fat control groups.

Blood inflammatory markers also tended to be lower in the lingonberry, blackcurrant, bilberry, and low fat groups compared to the high fat control.

How did the researchers interpret the results?

The researchers conclude that lingonberries fully or partially prevent the detrimental metabolic effects of a high-fat diet. Blackcurrants and bilberries had similar properties, but to a lesser extent.

They suggest that “the beneficial metabolic effects of lingonberries could be useful in preventing obesity and related disorders”.

Conclusion

This animal research explored how different berries might moderate the harmful effects of a high fat diet in an attempt to mimic the high fat diet now common in Western societies.

Of the berries tested, lingonberries came out top. Blackcurrants and bilberries weren’t that far behind, whereas acai berries fared worse than not eating any berries on some measures. It is important to note that all the groups (those eating berries and those not) gained a lot of weight and body fat due to the high fat diet, but those eating berries gained less in some cases.

Overall, the researchers suggest that lingonberries have beneficial metabolic effects that could be useful in preventing obesity and related conditions such as obesity, however this is largely speculative at this early stage in the research.

Due to the potential market of an “eat as much of you want without putting on weight drug” (as unlikely as that may be in reality), we expect that this study will lead to more work looking closely at the effects of lingonberries on the human metabolism.

The research has so far only examined possible effects in mice and has not looked at the effect of lingonberry consumption on the health of humans.